A conventional motor 100 includes a rotor part 101 having a rotor shaft 103 and a rotor magnet 104 and a stator part 102 which is disposed so as to face the rotor magnet 104 through a clearance as shown in FIG. 5. The rotor shaft 103 is rotatably supported by bearings 105, 110 and one end of the rotor shaft 103 is urged by a plate spring 107 in an axial direction through a ball 108.
The bearing 105 includes a ball 105a abutting with a fitting hole which is formed on the other end of the rotor shaft 103 and a ball holding body 105b for holding the ball 105a. The bearing 110 is a radial bearing for supporting the rotor shaft 103 in a radial direction and is disposed on the under side of the rotor magnet 104 in FIG. 5. A clearance is formed between the inner peripheral face of the bearing 110 and the outer peripheral face of the rotor shaft 101, and thus the rotor shaft 101 rotates smoothly without being locked (see Japanese Patent Laid-Open No. Hei 9-135562).
However, in the motor 100 shown in FIG. 5, the fluctuation occurs in the rotor shaft 101 due to the positioning errors or the like between the rotor magnet 104 and the stator part 102 when the motor is rotated, and noises are generated between the bearings 110, 105 or the like and the rotor shaft 103. It has been known that these noises are two different types of noise, i.e., striking noise and sliding noise.
The striking noise has been considered to be generated by the rotor shaft 101 that moves radially due to the clearance formed between the inner peripheral face of the bearing 110 and the outer peripheral face of the rotor shaft 103 and the rotor shaft 103 that strikes against the inner peripheral face of the bearing 110. When the rotor shaft 103 strikes the bearing 110, a rattling sound is generated. This indicates the generation of the striking noise. The sliding noise is considered to be generated when the ball 105a integrally rotated with the rotor shaft 103 slides to the ball holding body 105b and when the ball 108 integrally rotated with the rotor shaft 103 slides to the plate spring 107. Further, the sliding noise is considered to be generated between the rotor shaft 103 and the bearing 110 when the rotor shaft 103 is rotated.